Paid off 1949. In reserve 1949-1956. Broken up by Hughes Bolckow, Blyth, 1956.

Sirius's completion was delayed by bombing. She initially joined the Home Fleet, then went to the Mediterranean in August for Operation Pedestal. She was then ordered to the South Atlantic to patrol against Axis blockade runners on the Far East route, returning to Gibraltar in November for Operation Torch, the North African landings. As part of Force Q at Bone in December she harried Axis convoys to and from Tunisia until the Axis surrender in North Africa and then, as part of the 12th Cruiser Squadron, was at the invasion of Sicily, Operation Husky, in July. For the next few months she supported the army ashore, and in September took part in the occupation of Taranto before transferring to the Adriatic, where, on 5 October 1943, she helped annihilate a German convoy in the Dodecanese. Unfortunately, on 17 October, Sirius was badly damaged by bombs off Scarpunto, and sailed to Massawa for repairs. These were carried out between November 1943 and February 1944, before the ship returned to Britain for Operation Overlord, the Normandy landings, where she was part of the reserve of the Eastern Task Force. In August she returned to Mediterranean waters for the landings in the south of France, Operation Dragoon. She then served again in the Aegean, where, in October 1944, she was present during the reoccupation of Athens. Sirius remained with the Mediterranean Fleet, 15th Cruiser Squadron, postwar until 1946. After refit at Portsmouth in 1946, Sirius joined the 2nd Cruiser Squadron with the Home Fleet in March 1947. She paid off in 1949 and was put up for disposal in 1956. On 15 October 1956 Sirius arrived at the Blyth yard of Hughes Bolkow for breaking up.